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otonh210

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## Homework Statement

A 45kg figure skater is spinning on the toes of her skates at 1.0 rev/s. Her arms are outstretched as far as they will go/ In this orientation, the skater can be modeled as a cylindrical torso (40kg, 20cm average diameter, 160cm tall) plus two rod-like arms (2.5kg each, 66cm long) attached to the outside of the torso. The skater then raises her arms straight above her head, where she appears to be a 45kg, 20cm diameter, 200cm tall cylinder. What is her new rotation frequency, in revolutions per second?

## Homework Equations

L=Iw

Li=Lf

Ii = Ibody + 2 Iarm

## The Attempt at a Solution

I did conservation of L

(Ibody + 2 Iarm)(1 rev/s) = Iwholebody (wf)

Ibody = 1/2 Mr^2 = 1/2(40kg)(.1m)^2

Iarm = 1/3Mr^2 (?)

Iwholebody = 1/2Mr^2 = 1/2(45kg)(.1m)^2

When I did it this way, I got ~ 5.7 rev/s

The answer I am supposed to be getting is 3.5 rev/s

All the resources I am using to help me figure this out are not offering any new help.

Am I supposed to be using her height? Where?

Thank you very much.

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